1. Field of the Invention
The present invention relates to an impact sensing apparatus, and more particularly to an impact sensing apparatus which mechanically ignites an ignition element without electric power for use as a starting sensor of an anti-shock safety system such as an air-bag and a seatbelt tensioner.
2. Description of the Prior Art
A conventional impact sensing apparatus is disclosed, for example, in Japanese patent application laid-open publication No. 2 (1990)-249744. In this prior impact sensing apparatus, when a shock which is more than a predetermined value is applied from outside thereto, a weight is rotated and slid by the shock. Then, the engagement between a cam portion formed on the weight and a firing lever is released by the rotation and the sliding movement of the weight and the firing lever is rotated by the urging force of a spring. As a result, a firing pin formed on the firing lever projects outside of the housing in the opposite direction with respect to the applied direction of the shock through a hole portion which is formed on the right-angled wall of the housing. Then, the firing pin strikes an ignition element such as a primer. In the above conventional impact sensing apparatus, however, since the firing pin projects outside of the housing in the opposite direction with respect to the applied direction of the shock through the hole portion which is formed on the fight-angled wall of the housing, the stroke of the rotational motion of the firing lever is short. Therefore, it is not able to effectively utilize the urging force of the spring as a kinetic energy of the firing pin for striking the ignition element.